Re: [dpdk-dev] [PATCH v8 2/4] telemetry: fix socket path conflicts for in-memory mode

[Kevin Traynor]

On 12/10/2021 17:39, Bruce Richardson wrote:
When running using in-memory mode, multiple processes can use the same
runtime dir, leading to conflicts with the telemetry sockets in that
directory. We can resolve this by appending a suffix to each socket
beyond the first, with the suffix being an increasing counter value.
Each process uses the first unused socket counter value.
Fixes: 6dd571fd07c3 ("telemetry: introduce new functionality")

Reported-by: David Marchand <david.march...@redhat.com>
Signed-off-by: Bruce Richardson <bruce.richard...@intel.com>
Acked-by: Ciara Power <ciara.po...@intel.com>

Thanks Bruce, lgtm. Nice solution to keep existing name where possible 
and to give as predictable as you can names for others.

Acked-by: Kevin Traynor <ktray...@redhat.com>

---
  lib/telemetry/telemetry.c | 65 +++++++++++++++++++++++++++++----------
  1 file changed, 49 insertions(+), 16 deletions(-)

diff --git a/lib/telemetry/telemetry.c b/lib/telemetry/telemetry.c
index 48f4c7ba46..a7483167d4 100644
--- a/lib/telemetry/telemetry.c
+++ b/lib/telemetry/telemetry.c
@@ -457,28 +457,45 @@ create_socket(char *path)
  
  	struct sockaddr_un sun = {.sun_family = AF_UNIX};
        strlcpy(sun.sun_path, path, sizeof(sun.sun_path));
-       unlink(sun.sun_path);
+       TMTY_LOG(DEBUG, "Attempting socket bind to path '%s'\n", path);
+
        if (bind(sock, (void *) &sun, sizeof(sun)) < 0) {
                struct stat st;
  
-		TMTY_LOG(ERR, "Error binding socket: %s\n", strerror(errno));
-               if (stat(socket_dir, &st) < 0 || !S_ISDIR(st.st_mode))
+               TMTY_LOG(DEBUG, "Initial bind to socket '%s' failed.\n", path);
+
+               /* first check if we have a runtime dir */
+               if (stat(socket_dir, &st) < 0 || !S_ISDIR(st.st_mode)) {
                        TMTY_LOG(ERR, "Cannot access DPDK runtime directory: 
%s\n", socket_dir);
-               sun.sun_path[0] = 0;
-               goto error;
+                       close(sock);
+                       return -ENOENT;
+               }
+
+               /* check if current socket is active */
+               if (connect(sock, (void *)&sun, sizeof(sun)) == 0) {
+                       close(sock);
+                       return -EADDRINUSE;
+               }
+
+               /* socket is not active, delete and attempt rebind */
+               TMTY_LOG(DEBUG, "Attempting unlink and retrying bind\n");
+               unlink(sun.sun_path);
+               if (bind(sock, (void *) &sun, sizeof(sun)) < 0) {
+                       TMTY_LOG(ERR, "Error binding socket: %s\n", 
strerror(errno));
+                       close(sock);
+                       return -errno; /* if unlink failed, this will be 
-EADDRINUSE as above */
+               }
        }
  
  	if (listen(sock, 1) < 0) {
                TMTY_LOG(ERR, "Error calling listen for socket: %s\n", 
strerror(errno));
-               goto error;
+               unlink(sun.sun_path);
+               close(sock);
+               return -errno;
        }
+       TMTY_LOG(DEBUG, "Socket creation and binding ok\n");
  
  	return sock;
-
-error:
-       close(sock);
-       unlink_sockets();
-       return -1;
  }
  
  static void
@@ -511,8 +528,10 @@ telemetry_legacy_init(void)
                return -1;
        }
        v1_socket.sock = create_socket(v1_socket.path);
-       if (v1_socket.sock < 0)
+       if (v1_socket.sock < 0) {
+               v1_socket.path[0] = '\0';
                return -1;
+       }
        rc = pthread_create(&t_old, NULL, socket_listener, &v1_socket);
        if (rc != 0) {
                TMTY_LOG(ERR, "Error with create legcay socket thread: %s\n",
@@ -533,7 +552,9 @@ telemetry_legacy_init(void)
  static int
  telemetry_v2_init(void)
  {
+       char spath[sizeof(v2_socket.path)];
        pthread_t t_new;
+       short suffix = 0;
        int rc;
  
  	v2_socket.num_clients = &v2_clients;
@@ -544,15 +565,27 @@ telemetry_v2_init(void)
        rte_telemetry_register_cmd("/help", command_help,
                        "Returns help text for a command. Parameters: string 
command");
        v2_socket.fn = client_handler;
-       if (strlcpy(v2_socket.path, get_socket_path(socket_dir, 2),
-                       sizeof(v2_socket.path)) >= sizeof(v2_socket.path)) {
+       if (strlcpy(spath, get_socket_path(socket_dir, 2), sizeof(spath)) >= 
sizeof(spath)) {
                TMTY_LOG(ERR, "Error with socket binding, path too long\n");
                return -1;
        }
+       memcpy(v2_socket.path, spath, sizeof(v2_socket.path));
  
  	v2_socket.sock = create_socket(v2_socket.path);
-       if (v2_socket.sock < 0)
-               return -1;
+       while (v2_socket.sock < 0) {
+               /* bail out on unexpected error, or suffix wrap-around */
+               if (v2_socket.sock != -EADDRINUSE || suffix < 0) {
+                       v2_socket.path[0] = '\0'; /* clear socket path */
+                       return -1;
+               }
+               /* add a suffix to the path if the basic version fails */
+               if (snprintf(v2_socket.path, sizeof(v2_socket.path), "%s:%d",
+                               spath, ++suffix) >= 
(int)sizeof(v2_socket.path)) {
+                       TMTY_LOG(ERR, "Error with socket binding, path too 
long\n");
+                       return -1;
+               }
+               v2_socket.sock = create_socket(v2_socket.path);
+       }
        rc = pthread_create(&t_new, NULL, socket_listener, &v2_socket);
        if (rc != 0) {
                TMTY_LOG(ERR, "Error with create socket thread: %s\n",